The present invention relates to catalyst systems and their use in the polymerization of propylene.
Processes for preparing polyolefins with the aid of soluble, homogeneous catalyst systems comprising a transition metal component of the metallocene type and a cocatalyst component such as an aluminoxane, a Lewis acid or an ionic compound are known. These catalysts have a high activity and give polymers and copolymers having a narrow molar mass distribution.
In polymerization processes using soluble, homogeneous catalyst systems, thick deposits are formed on reactor walls and stirrers if the polymer is obtained as a solid. These deposits are formed by agglomeration of polymer particles whenever metallocene and/or cocatalysts are present in dissolved form in the suspension. Such deposits in the reactor systems have to be removed regularly since they quickly attain considerable thicknesses, have a high strength and prevent heat transfer to the cooling medium. Such homogeneous catalyst systems cannot be used in modern industrial polymerization processes in the liquid monomer or in the gas phase.
To avoid deposit formation in the reactor, it has been proposed that supported catalyst systems in which the metallocene and/or the aluminum compounds serving as cocatalyst are immobilized on an inorganic support material be used.
EP-A-0,576,970 discloses metallocenes and corresponding supported catalyst systems.
Highly active supported catalyst systems for preparing industrially important polyolefins having high tacticity and a high melting point, in particular polypropylenes, comprise ansa-metallocenes in racemic or pseudoracemic form and are known, for example, from EP-A-0,530,647; EP-A-0,576,970 and EP-A-0,653,433.
Ansa-Metallocenes are obtained in the synthesis as isomer mixtures (rac form and meso form or pseudo rac/pseudo meso form), so that an additional and complicated process step for separating rac and meso forms (or the pseudo forms) is necessary. A definition of the terms rac form and meso form may be found in Brinzinger et al., Journal of Organometallic Chemistry, 232 (1982) page 233 and Schlxc3x6gl, Top. Stereochem., 1 (1967) page 39 ff.
In addition, methylaluminoxane (MAO) as hitherto the most effective cocatalyst has the disadvantage of having to be used in a large excess. Such aluminoxanes are described, for example, in JACS 117 (1995), 6465-74, Organometallics 13 (1994), 2957-2969.
The preparation of cationic alkyl complexes opens a route to MAO-free catalysts having comparable activity in which the cocatalyst can be used in a virtually stochiometric amount.
Industrial utilization of metallocene catalysts necessitates, as described above, their conversion into a heterogeneous catalyst system in order to ensure an appropriate morphology of the resulting polymer. The application of cationic metallocene catalysts based on borate anions to supports is described in WO-91/09882. Here, the catalyst system is formed by application of a dialkyl-metallocene compound and a Brxc3x6nsted-acid, quaternary ammonium compound having a noncoordinating anion such as tetrakispentafluorophenylborate to an inorganic support. The support material is modified beforehand using a trialkylaluminum compound. A disadvantage of this process for application to a support is that only a small part of the metallocene used is immobilized by physisorbtion on the support material. When the catalyst system is introduced into the reactor, the metallocene can easily be leached from the support surface. This leads to a polymerization which occurs partly homogeneously, resulting in an unsatisfactory morphology of the polymer.
It is an object of the present invention to find an inexpensive, highly active catalyst system for the preparation of polypropylene having high tacticity and a high melting point and also to provide a simple and economical process for preparing such a catalyst system, which process requires no additional separation of rac and meso forms of the metallocene components present and does not use aluminoxanes such as methylaluminoxane (MAO) as cocatalyst.
We have found that this object is achieved by a catalyst system comprising at least one metallocene as rac/meso isomer mixture, at least one organoboroaluminum compound, at least one passivated support, at least one Lewis base and, if desired, at least one further organometallic compound.
The present invention accordingly provides a catalyst system comprising
a) at least one substituted metallocene of the formula A 
xe2x80x83where
R1 and R2 are identical or different and are each a hydrogen atom, a C1-C20-hydrocarbon group such as a C1-C20-alkyl group, preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, pentyl or hexyl, a C6-C14-aryl group or a C2-C20-alkenyl group, with the proviso that R1 is not methyl when R2 is hydrogen,
M1 is a transition metal of group 4, 5 or 6 of the Periodic Table of the Elements, for example titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum or tungsten, preferably titanium, zirconium or hafnium, particularly preferably zirconium,
A is a bridge of the formula 
xe2x80x83or xe2x95x90BR3, AIR3, xe2x80x94Sxe2x80x94, xe2x80x94SOxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x95x90NR3, xe2x95x90PR3, xe2x95x90P(O)R3, o-phenylene, 2,2xe2x80x2-biphenylene, where
M2 is carbon, silicon, germanium, tin, nitrogen or phosphorus, preferably carbon, silicon or germanium, in particular carbon or silicon,
o is 1, 2, 3 or 4, preferably 1 or 2,
R3 and R4 are identical or different and are each, independently of one another, a hydrogen atom, halogen, a C1-C20 group such as C1-C20-alkyl, in particular a methyl group, C6-C14-aryl, in particular a phenyl or naphthyl group, C1-C10-alkoxy, C2-C10-alkenyl, C7-C20-arylalkyl, C7-C20-alkylaryl, C6-C10-aryloxy, C1-C10-fluoroalkyl, C6-C10-haloaryl, C2-C10-alkynyl, C3-C20-alkylsilyl, for example trimethylsilyl, triethylsilyl or tert-butyldimethylsilyl, C3-C20-arylsilyl, for example triphenylsilyl, or C3-C20-alkylarylsilyl, for example dimethylphenylsilyl, diphenylsilyl or diphenyl-tert-butylsilyl, or R3 and R4 may together form a monocyclic or polycyclic ring system, and
A is preferably dimethylsilanediyl, dimethylgermanediyl, ethylidene, methylethylidene, 1,1-dimethylethylidene, 1,2-dimethylethylidene, tetramethylethylidene, isopropylidene, phenylmethylmethylidene, diphenylmethylidene, particularly preferably dimethylsilanediyl, dimethylgermanediyl or ethylidene,
X are identical or different and are each a hydrogen atom, a halogen atom such as fluorine, chlorine, bromine or iodine, a hydroxyl group, a C1-C10-alkyl group such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl or cyclohexyl, a C6-C15-aryl group such as phenyl or naphthyl, a C1-C10-alkoxy group such as methoxy, ethoxy or tert-butoxy, a C6-C15-aryloxy group, a benzyl group, an NR52 group, where R5 are identical or different and are each a C1-C10-alkyl group, in particular methyl and/or ethyl, a C6-C15-aryl group, a (CH3)3Si group, preferably a chlorine atom, a fluorine atom, a methyl group, a benzyl group or an NMe2 group, particularly preferably a chlorine atom or a methyl group,
where the ratio of rac isomer to meso isomer of the metallocene of the formula (A) in the novel catalyst system is from 1:10 to 2:1, preferably from 1:2 to 3:2,
b) at least one Lewis base of the formula I,
M3R6R7R8xe2x80x83xe2x80x83(I)
xe2x80x83where
R6, R7 and R8 are identical or different and are each a hydrogen atom, a C1-C20-alkyl group, a C1-C20-haloalkyl group, a C6-C40-aryl group, a C6-C40-haloaryl group, a C7-C40-alkylaryl group or a C7-C40-arylalkyl group, where two radicals or all three radicals R6, R7 and R8 may be joined to one another via C2-C20 units and M3 is an element of main group V of the Periodic Table of the Elements,
c) a support,
d) at least one organoboroaluminum compound which is made up of units of the formula II
Ri9M4xe2x80x94Oxe2x80x94M4Rj10xe2x80x83xe2x80x83(II)
xe2x80x83where
R9 and R10 are identical or different and are each a hydrogen atom, a halogen atom, a C1-C40 group, in particular C1-C20-alkyl, C1-C20-haloalkyl, C1-C10-alkoxy, C6-C20-aryl, C6-C20-haloaryl, C6-C20-aryloxy, C7-C40-arylalkyl, C7-C40-haloarylalkyl, C7-C40-alkylaryl or C7-C40-haloalkylaryl, or R9 may be an xe2x80x94OSiR3 group, where R are identical or different and are as defined for R9,
M4 are identical or different and are each an element of main group 3 of the Periodic Table of the Elements and
i and j are each an integer 0, 1 or 2,
and is covalently bound to the support,
and, if desired,
e) an organometallic compound of the formula V
[M5R11p]kxe2x80x83xe2x80x83(V)
xe2x80x83where
M5 is an element of main group I, II or III of the Periodic Table of the Elements,
R11 are identical or different and are each a hydrogen atom, a halogen atom or a C1-C40 group, in particular a C1-C20-alkyl group, a C6-C40-aryl group, a C7-C40-arylalkyl group or a C7-C40-alkylaryl group,
p is an integer from 1 to 3 and
k is an integer from 1 to 4.
The Lewis bases of the formula (I) are preferably ones in which M3 is nitrogen or phosphorus. Examples of such compounds are triethylamine, triisopropylamine, triisobutylamine, tri(n-butyl)amine, N,N-dimethylaniline, N,N-diethylaniline, N,N-2,4,6-pentamethylaniline, dicyclohexylamine, pyridine, pyrazine, triphenylphosphine, tri(methylphenyl)phosphine and tri(dimethylphenyl)phosphine.
The support component of the catalyst system of the present invention can be any organic or inorganic, inert solid, in particular a porous support such as talc, inorganic oxides and finely divided polymer powders (e.g. polyolefins).
Suitable inorgainc oxides may be found among the oxides of elements of groups 2,3,4,5,13,14,15 and 16 of the Periodic Table of the Elements. Examples of oxides preferred as support include silicon dioxide, aluminum oxide and mixed oxides of the two elements and corresponding oxide mixtures. Other inorganic oxides, which may be used either alone or in combination with the abovementioned preferred oxidic supports, are for example, MgO, ZrO2 , TiO2 or B2O3, to name only a few.
The support materials used have a specific surface area in the range from 10 to 1000 m2/g, a pore volume in the range from 0.1 to 5 ml/g and a mean particle size of from 1 to 500 xcexcm. Preference is given to supports having a specific surface area in the range from 50 to 500 xcexcm, a pore volume in the range from 0.5 to 3.5 ml/g and a mean particle size in the range from 5 to 350 xcexcm. Particular preference is given to supports having a specific surface area in the range from 200 to 400 m2/g, a pore volume in the range from 0.8 to 3.0 ml/g and a mean particle size of from 10 to 200 xcexcm.
If the support material used naturally has a low moisture content or residual solvent content, dehydration or drying prior to use can be omitted. If this is not the case, for example when using silica gel as support material, dehydration or drying is advisable. Thermal dehydration or drying of the support material can be carried out under reduced pressure with simultaneous inert gas blanketing (e.g. nitrogen). The drying temperature is in the range from 100 to 1000xc2x0 C., preferably from 200 to 800xc2x0 C. In this case, the parameter pressure is not critical. The duration of the drying process can be from 1 to 24 hours. Shorter or longer drying times are possible, provided that equilibrium with the hydroxyl groups on the support surface can be established under the conditions selected, which normally takes from 4 to 8 hours.
Dehydration or drying of the support material can also be carried out by chemical means by reacting the absorbed water and the hydroxyl groups on the surface with suitable passivating agents. The reaction with the passivating reagent can convert all or some of the hydroxyl groups into a form which leads to no adverse interaction with the catalytically active centers. Suitable passivating agents are, for example, silicon halides and silanes, e.g. silicon tetrachloride, chlorotrimethylsilane, dimethylaminotrichlorosilane, or organometallic compounds of aluminum, boron and magnesium, for example trimethylaluminum, triethylaluminum, triisobutylaluminum, triethylborane, dibutylmagnesium. Chemical dehydration or passivation of the support material is carried out, for example, by reacting a suspension of the support material in a suitable solvent in the absence of air and moisture with the passivating reagent in pure form or as a solution in a suitable solvent. Suitable solvents are, for example, aliphatic or aromatic hydrocarbons such as pentane, hexane, heptane, toluene or xylene. Passivation is carried out at from 25xc2x0 C. to 120xc2x0 C., preferably from 50 to 70xc2x0 C. Higher and lower temperatures are possible. The reaction time is from 30 minutes to 20 hours, preferably from 1 to 5 hours. After chemical dehydration is complete, the support material is isolated by filtration under inert conditions, washed one or more times with suitable inert solvents as have been described above and subsequently dried in a stream of inert gas or under reduced pressure.
Organic support materials such as finely divided polyolefin powders (e.g. polyethylene, polypropylene or polystyrene) can also be used and should likewise be freed of adhering moisture, solvent residues or other impurities by means of appropriate purification and drying operations prior to use.
The catalyst system of the present invention comprises, as cocatalytically active chemical compound, at least one organoboroaluminum compound comprising units of the formula (II). Preference is given to compounds of the formula (II) in which M3 is boron or aluminum.
The compound comprising units of the formula (II) may be in the form of a monomer or a linear, cyclic or cage-like oligomer. It is also possible for two or more chemical compounds comprising units of the formula (II) to form dimers, trimers or higher associates with one another by means of Lewis acid-Lewis base interactions or condensation reactions. It is also possible to use mixtures of the compounds described.
Preferred cocatalytically active organoboroaluminum compounds d) correspond to the formulae (III) and (IV), 
where R9 and R10 are as defined under formula (II).
Examples of cocatalytically active compounds of the formulae (III) and (IV) are 
The organometallic compounds of the formula (IV) are preferably uncharged Lewis acids in which M5 is lithium, magnesium and/or aluminum, in particular aluminum.
Examples of preferred organometallic compounds of the formula (V) are trimethylaluminum, triethylaluminum, triisopropylaluminum, trihexylaluminum, trioctylaluminum, tri-n-butylaluminum, tri-n-propylaluminum, triisoprenaluminum, dimethylaluminum monochloride, diethylaluminum monochloride, diisobutylaluminum monochloride, methylaluminum sesquichloride, ethylaluminum sesquichloride, dimethylaluminum hydride, diethylaluminum hydride, diisopropylaluminum hydride, dimethylaluminum trimethylsiloxide, dimethylaluminum triethylsiloxide, phenylalane, pentafluorophenylalane and o-tolylalane.
The metallocene of the formula (A) is preferably one of the following compounds:
dimethylsilanediylbis(2-methyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)hafnium dichloride
dimethylsilanediylbis(2-methyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)titanium dichloride
dimethylsilanediylbis(2-methyl-4-(4xe2x80x2-methylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-(4xe2x80x2-ethylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-(4xe2x80x2-n-propylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-(4xe2x80x2-isopropylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-(4xe2x80x2-n-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-(4xe2x80x2-hexylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-(4xe2x80x2-sec-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-phenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-(4xe2x80x2-methylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-(4xe2x80x2-ethylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-(4xe2x80x2-n-propylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-(4xe2x80x2-isopropylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-(4xe2x80x2-n-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-(4xe2x80x2-hexylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-(4xe2x80x2-pentylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-(4xe2x80x2-cyclohexylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-(4xe2x80x2-sec-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-propyl-4-phenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-propyl-4-(4xe2x80x2-methylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-propyl-4-(4xe2x80x2-ethylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-propyl-4-(4xe2x80x2-n-propylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-propyl-4-(4xe2x80x2-isopropylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-propyl-4-(4xe2x80x2-n-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-propyl-4-(4xe2x80x2-hexylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-propyl-4-(4xe2x80x2-cyclohexylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-propyl-4-(4xe2x80x2-sec-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-propyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-butyl-4-phenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-butyl-4-(4xe2x80x2-methylphenyl) indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-butyl-4-(4xe2x80x2-ethylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-butyl-4-(4xe2x80x2-n-propylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-butyl-4-(4xe2x80x2-isopropylphenyl) indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-butyl-4-(4xe2x80x2-n-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-butyl-4-(4xe2x80x2-hexylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-butyl-4-(4xe2x80x2-cyclohexylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-butyl-4-(4xe2x80x2-sec-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-n-butyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-hexyl-4-phenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-hexyl-4-(4xe2x80x2-methylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-hexyl-4-(4xe2x80x2-ethylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-hexyl-4-(4xe2x80x2-n-propylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-hexyl-4-(4xe2x80x2-isopropylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-hexyl-4-(4xe2x80x2-n-butylphenyl)zirconium dichloride
dimethylsilanediylbis(2-hexyl-4-(4xe2x80x2-hexylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-hexyl-4-(4xe2x80x2-cyclohexylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-hexyl-4-(4xe2x80x2-sec-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-hexyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium dichloride
dimethylsilanediylbis(2-methyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium bis(dimethylamide)
dimethylsilanediylbis(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)dibenzylzirconium
dimethylsilanediylbis(2-methyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)dimethylzirconium
imethylgermanediylbis(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium dichloride
dimethylgermanediylbis(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl) hafnium dichloride
dimethylgermanediylbis(2-propyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)titanium dichloride
dimethylgermanediylbis(2-methyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium dichloride
ethylidenebis(2-ethyl-4-phenyl)indenyl)zirconium dichloride
ethylidenebis(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium dichloride
ethylidenebis(2-n-propyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium dichloride
ethylidenebis(2-n-butyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)titanium dichloride
ethylidenebis(2-hexyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)dibenzylzirconium
ethylidenebis(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)dibenzylhafnium
ethylidenebis(2-methyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)dibenzyltitanium
ethylidenebis(2-methyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium dichloride
ethylidenebis(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)dimethylhafnium
ethylidenebis(2-n-propyl-4-phenyl)indenyl)dimethyltitanium
ethylidenebis(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium bis(dimethylamide)
ethylidenebis(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl) hafnium bis(dimethylamide)
ethylidenebis(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)titanium bis(dimethylamide)
methylethylidenebis(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium dichloride
methylethylidenebis(2-ethyl-4-(4xe2x80x2-tert-butylphenyl) indenyl)hafnium dichloride
phenylphosphinediyl(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl)zirconium dichloride
phenylphosphinediyl(2-methyl-4-(4xe2x80x2-tert-butylphenyl)indenyl) zirconium dichloride
phenylphosphinediyl(2-ethyl-4-(4xe2x80x2-tert-butylphenyl)indenyl) zirconium dichloride
Further examples of metallocenes which can be used according to the present invention are analogues of the above metallocenes in which the zirconium fragment xe2x80x9czirconium dichloridexe2x80x9d is replaced by
zirconium monochloride mono(2,4-di-tert-butylphenoxide)
zirconium monochloride mono(2,6-di-tert-butylphenoxide)
zirconium monochloride mono(3,5-di-tert-butylphenoxide)
zirconium monochloride mono(2,6-di-sec-butylphenoxide)
zirconium monochloride mono(2,4-di-methylphenoxide)
zirconium monochloride mono(2,3-di-methylphenoxide)
zirconium monochloride mono(2,5-di-methylphenoxide)
zirconium monochloride mono(2,6-di-methylphenoxide)
zirconium monochloride mono(3,4-di-methylphenoxide)
zirconium monochloride mono(3,5-di-methylphenoxide)
zirconium monochloride monophenoxide
zirconium monochloride mono(2-methylphenoxide)
zirconium monochloride mono(3-methylphenoxide)
zirconium monochloride mono(4-methylphenoxide)
zirconium monochloride mono(2-ethylphenoxide)
zirconium monochloride mono(3-ethylphenoxide)
zirconium monochloride mono(4-ethylphenoxide)
zirconium monochloride mono(2-sec-butylphenoxide)
zirconium monochloride mono(2-tert-butylphenoxide)
zirconium monochloride mono(3-tert-butylphenoxide)
zirconium monochloride mono(4-sec-butylphenoxide)
zirconium monochloride mono(4-tert-butylphenoxide)
zirconium monochloride mono(2-isopropyl-5-methylphenoxide)
zirconium monochloride mono(4-isopropyl-3-methylphenoxide)
zirconium monochloride mono(5-isopropyl-2-methylphenoxide)
zirconium monochloride mono(5-isopropyl-3-methylphenoxide)
zirconium monochloride mono(2,4-bis-(2-methyl-2-butyl)phenoxide)
zirconium monochloride mono(2,6-di-tert-butyl-4-methylphenoxide)
zirconium monochloride mono(4-nonylphenoxide)
zirconium monochloride mono(1-naphthoxide)
zirconium monochloride mono(2-naphthoxide)
zirconium monochloride mono(2-phenylphenoxide)
zirconium monochloride mono(tert-butoxide)
zirconium monochloride mono(N-methylanilide)
zirconium monochloride mono(2-tert-butylanilide)
zirconium monochloride mono(tert-butylamide)
zirconium monochloride mono(di-isopropylamide)
zirconium monochloride monomethyl
zirconium monochloride monobenzyl
zirconium monochloride mononeopentyl.
Preference is also given to the corresponding dimethylzirconium compounds and the corresponding xcex74-butadienezirconium compounds, and also the corresponding compounds having 1,2-(1-methylethanediyl), 1,2-(1,1-dimethylethanediyl) and 1,2(1,2-dimethylethanediyl) bridges.
The ratio of rac isomer to meso isomer of the metallocene component of the formula (A) in the catalyst system of the present invention is in the range from 1:10 to 2:1, preferably from 1:2 to 3:2.
The methods of preparing metallocenes of the formula (A) are described in detail in, for example, Journal of Organometallic Chem. 288 (1985) 63-67 and in the documents cited therein.
The catalyst system of the present invention is obtainable by reaction of a Lewis base of the formula (I) and an organoboroaluminum compound made up of units of the formula (II) with a support. This is followed by reaction with a solution or suspension of one or more metallocene compounds of the formula (VI) and, if desired, one or more organometallic compounds of the formula (V).
The activation of the catalyst system can be carried out either before introduction into the reactor or else only in the reactor itself. The present invention also provides a process for preparing polyolefins. The addition of a further chemical compound which is introduced as additive before the polymerization can also be advantageous.
To prepare the catalyst system of the present invention, the support material is suspended in an organic solvent. Suitable solvents are aromatic or aliphatic solvents, for example hexane, heptane, toluene or xylene, or halogenated hydrocarbons such as methylene chloride or halogenated aromatic hydrocarbons such as o-dichlorobenzene. The support can be pretreated beforehand with a compound of the formula (V). Subsequently, one or more compounds of the formula (I) is/are added to this suspension, with the reaction time being able to be from 1 minute to 48 hours, preferably from 10 minutes to 2 hours. The reaction solution can be isolated and subsequently resuspended or else can be reacted directly with a cocatalytically active organoboroaluminum compound made up of units of the formula (II). The reaction time is from 1 minute to 48 hours, preferably from 10 minutes to 2 hours. Preference is given to using from 1 to 4 equivalents of a Lewis base of the formula (I) per equivalent of a cocatalytically active compound made up of units of the formula (II). Particular preference is given to using one equivalent of a Lewis base of the formula (I) per equivalent of a cocatalytically active compound made up of units of the formula (II). The reaction product of this reaction is a metallocenium-forming compound which is covalently bound to the support material. This will hereinafter be referred to as modified support material. The reaction mixture is subsequently filtered and the solid is washed with one of the abovementioned solvents. The modified support material is then dried in a high vacuum. After drying, the modified support material can be resuspended and after-treated with a compound of the formula (V). However, the compound of the formula (V) can also be added before filtration and drying of the modified support material.
The application of one or more metallocene compounds, preferably ones of the formula (A), and one or more organometallic compounds of the formula (V) to the modified support material is preferably carried out by dissolving or suspending one or more metallocene compounds of the formula (A) in one of the above-described solvents and subsequently reacting it with one or more compounds of the formula (V) which is/are likewise in dissolved or suspended form. The stochiometric ratio of metallocene compound of the formula (A) to an organometallic compound of the formula (V) is from 100:1 to 10xe2x88x924:1. The ratio is preferably from 1:1 to 10xe2x88x922:1. The modified support material can either be placed directly in the polymerization reactor or in a reaction flask in one of the abovementioned solvents. A mixture of a metallocene compound of the formula (A) and an organometallic compound of the formula (V) is then added. However, if desired, one or more metallocene compounds of the formula (A) can also be added to the modified support material without a prior addition of an organometallic compound of the formula (V).
The ratio of modified support to a metallocene compound of the formula (A) is preferably from 10 g:1 xcexcmol to 10xe2x88x922 g:1 xcexcmol. The stochiometric ratio of metallocene compound of the formula (A) to the supported cocatalytically active organoboroaluminum compound comprising units of the formula (II) is from 100:1 to 10xe2x88x924:1, preferably from 1:1 to 10xe2x88x922:1.
The supported catalyst system can be used directly for polymerization. However, it is also possible to remove the solvent and to resuspend the catalyst system for use in the polymerization. The advantage of this activation method is that it offers the option of allowing the polymerization-active catalyst system to be formed only in the reactor itself. This prevents partial decomposition from occurring during introduction of the air-sensitive catalyst.
The supported catalyst system prepared in this way can either be used directly for the polymerization of propylene or be prepolymerized using one or more olefinic monomers before it is used in a polymerization process. The prepolymerization procedure for supported catalyst systems is described, for example, in WO 94/28034.
The present invention also provides a process for preparing polypropylene by polymerization of propylene in the presence of the novel catalyst system comprising at least one transition metal component of the formula (A). For the purposes of the present invention, the term polymerization encompasses both homopolymerization and copolymerization, but refers in particular to homopolymerization of propylene.
The polymerization is carried out at from xe2x88x9260 to 300xc2x0 C., preferably from 50 to 200xc2x0 C., very particularly preferably 50xe2x88x9280xc2x0 C. The pressure is from 0.5 to 2000 bar, preferably from 5 to 64 bar.
The polymerization can be carried out in solution, in bulk, in suspension or in the gas phase, continuously or batchwise, in one or more stages.
The catalyst system of the present invention can be used as sole catalyst component for the polymerization of propylene, but is preferably used in combination with at least one alkyl compound of an element of main groups I to III of the Periodic Table, e.g. an aluminum alkyl, magnesium alkyl or lithium alkyl or an aluminoxane. The alkyl compound is added to the monomer or suspension medium and serves to free the monomer of substances which can impair the catalyst activity. The amount of alkyl compound added depends on the quality of the monomers used.
As molar mass regulator and/or to increase the activity, preference is given to adding hydrogen.
In addition, a mixture of a metal salt of Medialan acid, a metal salt of anthranilic acid and a polyamine can be used as antistatic, as described in EP-A-0,636,636.
Commercially available products such as Stadis(copyright) 450 from DuPont, namely a mixture of toluene, isopropanol, dodecylbenzenesulfonic acid, a polyamine, a copolymer of 1-decene and SO2 and also 1-decene or ASA(copyright)-3 from Shell and ARU5R(copyright) 163 from ICI can likewise be used.
The antistatic is preferably used as a solution; in the preferred case of Stadis(copyright) 450, preference is given to using from 1 to 50% by weight of this solution, preferably from 5 to 25% by weight, based on the mass of the supported catalyst used (support together with covalently bound metallocenium-forming compound and one or more metallocene compounds, e.g. of the formula A). The amounts of antistatic required may, however, vary within a wide range depending on the type of antistatic used.
The actual polymerization is preferably carried out in liquid monomer (bulk) or in the gas phase.
The antistatic can be introduced into the polymerization at any point in time. In an example of a preferred procedure, the supported catalyst system is resuspended in an organic solvent, preferably alkanes such as heptane or isododecane. It is subsequently introduced into the polymerization autoclave while stirring. The antistatic is then metered in. The polymerization is carried out at from 0 to 100xc2x0 C. In a further preferred procedure, the antistatic is introduced into the polymerization autoclave before addition of the supported catalyst system. The resuspended supported catalyst system is subsequently introduced while stirring at from 0 to 100xc2x0 C. The polymerization time can be in the range from 0.1 to 24 hours. Preference is given to a polymerization time in the range from 0.1 to 5 hours.
The polypropylenes prepared using the catalyst system of the present invention display a uniform particle morphology and contain no fines. No deposits or caked material occur in the polymerization using the catalyst system of the present invention.
The catalyst system of the present invention gives polypropylenes having extraordinarily high stereospecificity and regiospecificity.
Particular measures of the stereospecificity and regiospecificity of polypropylene are the triad tacticity (TT) and the proportion of 2-1-inserted propene units (RI), both of which can be determined from the 13C-NMR spectra.
The 13C-NMR spectra are measured in a mixture of hexachlorobutadiene and d2-tetrachloroethane at elevated temperature (365 K). All 13C-NMR spectra of the polypropylene samples measured are calibrated on the basis of the resonance signal of d2-tetrachloroethane (xcex4=73.81 ppm).
To determine the triad tacticity of polypropylene, the methyl resonance signals in the 13C-NMR spectrum in the range from 23 to 16 ppm are examined; cf. J. C. Randall, Polymer Sequence Determination: Carbon-13 NMR Method, Academic Press New York 1978; A. Zambelli, P. Locatelli, G. Bajo, F. A. Bovey, Macromolecules 8 (1975), 687-689; H. N. Cheng, J. A. Ewen, Makromol. Chem. 190 (1989), 1931-1943. Three successive 1-2-inserted propene units whose methyl groups are located on the same side in the xe2x80x9cFischer projectionxe2x80x9d are referred to as mm triads (xcex4=21.0 ppm to 22.0 ppm). If only the second methyl group of the three successive propene units points to the other side, one speaks of an rr triad (xcex4=19.5 ppm to 20.3 ppm), and if only the third methyl group of the three successive propene units points to the other side, one speaks of an mr triad (xcex4=20.3 ppm to 21.0 ppm). The triad tacticity is calculated according to the following formula:
TT(%)=mm/(mm+mr+rr)xc3x97100
If one propene unit is inserted inversely into the growing polymer chain, this is referred to as a 2-1-insertion; cf. T. Tsutsui, N. Ishimaru, A. Mizuno, A. Toyota, N. Kashiwa, Polymer 30, (1989), 1350-56. The following different structural arrangements are possible: 
The proportion of 2-1-inserted propene units (RI) can be calculated according to the following formula:
RI(%)=0.5Ixcex1,xcex2(Ixcex1,xcex1+Ixcex1,xcex2+Ixcex1,xcex2)xc3x97100,
where
Ixcex1,xcex1 is the sum of the intensities of the resonance signals at xcex4=41.84, 42.92 and 46.22 ppm,
Ixcex1,xcex2 is the sum of the intensities of the resonance signals at xcex4=30.13, 32.12, 35.11 and 35.57 ppm and
Ixcex1,xcex4 is the intensity of the resonance signal at xcex4=37.08 ppm.
The isotactic polypropylene which has been prepared using the catalyst system of the present invention has a proportion of 2-1-inserted propene units RI of  less than 0.5% at a triad tacticity TT of  greater than 98.0% and a melting point of  greater than 153xc2x0 C.; Mw/Mn, of the polypropylene prepared according to the present invention is in the range from 2.5 to 3.5.
The propylene copolymers which can be prepared using the catalyst system of the present invention have a significantly higher molar mass than those of the prior art. At the same time, such copolymers can be prepared with high productivity at industrially relevant process parameters without deposit formation by use of the catalyst system of the present invention.
The polypropylene prepared by the process of the present invention is particularly suitable for producing hard and stiff shaped bodies having a high tensile strength, e.g. fibers, filaments, injection-molded parts, films, sheets or large hollow bodies (e.g. pipes).
The following examples illustrate the invention but do not restrict its scope.
General information: preparation and handling of the compounds were carried out with exclusion of air and moisture under argon (Schlenk technique). All solvents required were dried before use by boiling for a number of hours over suitable desiccants and subsequent distillation under argon.